Use of Profilers for Studying Java Dynamic Optimizations
Presented at Midwest Instruction and Computing Symposium 2009.
Java differs from many common programming languages in that Java programs are first compiled to platform-independent bytecode. Java bytecode is run by a program called the Java Virtual Machine (JVM). Because of this approach, Java programs are often optimized dynamically (i.e. at run-time) by the JVM. A just-in-time compiler (JIT) is a part of the JVM that performs dynamic optimizations.
Our research goal is to be able to detect and study dynamic optimizations performed by a JIT using a profiler. A profiler is a programming tool that can track the performance of another program. A challenge for use of profilers for Java is a possible interaction between the profiler and the JVM, since the two programs are running at the same time. We show that profiling a Java program may disable some dynamic optimizations as a side effect in order to record information about those methods.
In this paper we examine interactions between a profiler and dynamic optimizations by studying the information collected by the profiler and program run-time measurements without and without profiling. We use Java HotSpot(TM) JVM by Sun Microsystems as a JVM with an embedded JIT and HPROF profiling tool. The paper details the testing methodology and presents the results and the conclusions.